1. Field of the Invention
The present invention relates to nonwoven fabrics which is bulky and has a soft touch or feeling, and a method for producing the same nonwoven fabrics.
2. Statement of the Prior Art
Many years have elapsed since there were known in the art the side-by-side or sheath-core type polypropylene base heat-adhesive composite fibers, which comprised two components having different melting points, and had a considerable portion, e.g., one half or more portion of their surfaces occupied by the component having a lower melting point, and the nonwoven fabrics made thereof. In the meantime, various improvements have been achieved. As disclosed in, e.g., Japanese Patent Publication No. 52-12830, Japanese Patent Laid-Open Publication No. 58-136867 and Japanese Patent Laid-Open Publication No. 58-180614, such improvements have primarily aimed at improving the shrink properties of a web in processing the fibers into a nonwoven fabric by heating and enhancing the strength, bulkiness and like factors of the resulting nonwoven fabric, and appreciable outcomes have been attained, but, referring to the bulkiness, any satisfactory outcome has been not yet achieved.
Hitherto, any appreciable outcome has been not attained in terms of not only the bulkiness but also the touch or feeling of nonwoven fabrics obtained from the polypropylene base heat-adhesive composite fibers by a heat treatment. Improvements in touch or feeling have been attempted as by using fine deniers or increasing the proportion of other fibers to be mixed with the composite fibers, such as rayon or wool, but have not still resulted in any product excelling in bulkiness and softness. The situation being like this, a strong demand for further improvements in the bulkiness and softness of nonwoven fabrics intended for purposes such as paper diapers or sanitary materials is not satisfied. Thus, it is strongly desired to meet such a demand.